1. Field of the Invention
This invention relates to a continuous packaging machine for successively packaging articles to be packaged by use of a web of a longitudinally prefolded film made of a synthetic resin sheet or synthetic resin laminated sheet, and more particularly to a continuous packaging machine in which a prefolded and firmly contacted film may be easily opened.
2. Prior Art
In the conventional art, a continuous automatic packaging machine is proposed as disclosed for example in JP, A sho 47-29087 (Japanese Patent Publication of Unexamined Application) that a guide board of a generally isosceles triangle is disposed to contact with the upper surface of a packaging film which is continuously drawn out horizontally from a winded roll, the packaging film is led from the two sides of the guide board to a generally vertical direction and after it is continuously prefolded through a guide roller, the prefolded film is opened and inverted to change the feed direction thereof, and after package articles are successively inserted into the opening of the prefolded film, the opening thereof is automatically sealed along the periphery of the package articles.
The prefolded film opening mechanism has however not been used as disclosed for example in U.S. Pat. No. 3,583,888 (1971), since it has been difficult to insert the package articles into the opening of the prefolded film by means of a simple device. In recent years, an automatic packaging machine is proposed and used for example in Japanese Utility Model sho 60-20567, that a web of a prefolded and rolledly winded film is continuously drawnout and opened through a film opening device while the prefolded film is inverted, a thin belt conveyor is disposed in the film opening device, and after package articles are intermittently introduced into the prefolded and opened film, the opening of the prefolded film is sealed by means of a L-shaped sealer. This means that since a considerably devised thin belt conveyor is inserted into the opening of the prefolded film, the package articles may be easily and precisely inserted into the opening of the prefolded film.
Many films of various qualities and structures are produced in the recent years and used as the packaging materials. There are various films, for example thick film such as an air cap, a laminated film, an adhesive film and the like.
However, after these films are prefolded and winded to provide a roll, when these prefolded films are opened while being drawnout, the static electricity generated between the adjacent surfaces of the prefolded film by the contact friction with guide rollers in winding and feeding, so that the blocking between the adjacent surfaces of the prefolded film due to the static electricity becomes hard to disturb the smooth opening of the prefolded film.
Accordingly, in order to remove these electrostatic troubles, an electrostatic charge preventing agent has been added to the film in manufacturing of the conventional film. However, in packaging of foods, the electrostatic charge preventing agent added to film is unfavourable by reason of health. Hence, the electrostatic charge removing means is directly connected to guide rollers for perfolded film. In this electrostatic charge removing means, it is also an actual practice that expectant results can not be obtained in case of the prefolded film. In order to dissolve the inconveniences due to the generation of this static electricity, it is required to remove blocking of the packaging material such as the prefolded film before opening thereof, so as to be able to carry out the continuous automation.